1. Field
The present embodiments relate to a capacitive pressure sensor and a method of manufacturing the same.
2. Related Art
Generally, a capacitive pressure sensor includes a substrate that has a pressure-sensitive diaphragm as a movable electrode and a substrate that has a fixed electrode. The substrates are bonded to each other at a predetermined gap between the pressure-sensitive diaphragm and the fixed electrode. In the capacitive pressure sensor, if pressure is applied to the pressure-sensitive diaphragm, the pressure-sensitive diaphragm is deformed, and the gap between the pressure-sensitive diaphragm and the fixed electrode changes accordingly. The change of the gap causes a change in capacitance between the pressure-sensitive diaphragm and the fixed electrode. Thus, a change in pressure is detected using the change of capacitance.
The above-described capacitive pressure sensor is disclosed in JP-A-8-75582, for example. As shown in FIG. 5, in the capacitive pressure sensor, a glass substrate 2 that has a fixed electrode 3 is disposed on a support substrate 1. A silicon substrate 4 has a diaphragm 4a that is bonded to the glass substrate 2. In the capacitive pressure sensor, a lead electrode 5 for the fixed electrode 3 is patterned on the glass substrate 2, and thus the lead electrode 5 is disposed in a bonded region of the glass substrate 2 and the silicon substrate 4.
However, in this structure, since the lead electrode 5 is located near the diaphragm 4a, parasitic capacitance other than capacitance between the diaphragm 4a and the fixed electrode 3 is large, and thus sensitivity of the capacitive pressure sensor is likely to be degraded. In addition, since the lead electrode 5 is disposed in the bonded region of the glass substrate 2 and the silicon substrate 4, airtightness inside a cavity between the diaphragm 4a and the fixed electrode 3 is reduced.